My home state publishes a list on invasive species for Massachusetts, and also defines which criteria a plant has to meet to be labeled “invasive”:

1. It is not native to Massachusetts
2. Must have the “biologic potential for rapid and widespread dispersion and establishment”
3. Must have the “biologic potential for dispersing over spatial gaps away from the site of introduction”
4. Must have the “biologic potential for existing in high numbers” away from gardens
5. Must have been introduced to Massachusetts already

The real text is a bit more cumbersome and bureaucratic – but we get the idea. There are tons of species on the lists, but here are a few from the list I would add to my list (this is arbitrary and based on my very personal experiences as a gardener at a single spot in Massachusetts – you might have a different opinion; it is worthwhile finding the list of invasive plants for your state!):

1. Japanese barberry – it stayed a single beautiful bush in my garden. But of course I can’t know to which places birds dispersed its seeds
2. Bittersweet. There are two bittersweets, with orange berries. One Celastrus scandens, the "American bittersweet" is non-invasive. The Asian or Oriental bittersweet is Celastrus orbiculatus, highly invasive. And it is the plant I called euonymus which I was familiar with from Europe. It seems, celastrus and euonymus are related species, and it is really the Celastrus orbiculatus that is so overly invasive. This vine’s berries are spread by birds, and the plant can strangle even trees. One of the worst I know – I would not plant it, and I am hacking it down wherever I meet it.
3. Purple loosestrife: Years ago, I bought a “butterfly bush” by mail order. It turned out to be purple loosestrife. As much as I try to eradicate it, it comes always up somewhere.
4. Wild rose (Rosa multiflora) is pretty while in bloom. But it flowers only once, and after flowering I always cut it of so it doesn’t set seeds. The rootstock, however – I’ll never get it out of my garden again.
5. Privet (Ligustrum vulgare) – it was in my garden when I moved in. It also might be another species as they are notoriously hard to identify. As often as I cut it back, it always pops up again.
6. Pennisetum, a vertically striped grass. Beautiful white and green. It is not invasive according to the Massachusetts definition, but like wisteria, it wants to take over my garden. There is a horizontally striped grass (Miscanthus sinensis) that might also become invasive – luckily, I never planted it.
7. White mulberry (Morus alba). Twice I planted a mulberry tree in my garden – mail orders. Twice they were not what they were advertised at: black mulberries. I wanted one in my garden desperately so that for once we can harvest our cherries before the birds do. Twice I had to hack down the tree because it grew as fast as Jack’s beanstalk – and did not deliver.

Sorry, compiling all this, takes longer than thought. In the next installment, we will hopefully discover the medicinal value of some of these invasive plants – the idea being, if we harvest and eat them, they will be less invasive.